N-type photosensitive member for electrophotography

ABSTRACT

A photosensitive layer for electrophotography is composed of SeTe alloy containing less than 3 percent by weight of Te and the Te is in a form of selenium-tellurium bond, and the Se-Te alloy has a polarity of N-type.

United States Patent Kondo et a1.

[111 3,816,116 June 11, 1974 N-TYPE PHOTOSENSITIVE MEMBER FOR ELECTROPHOTOGRAPHY Inventors: Hideyo Kondo, Tone-machi; Tatsuo Masaki; Nobuo Kitajirna, both of Tokyo, all of Japan Canon Kabushiki Kaisha, Tokyo, Japan Filed: Dec. 23, 1971 Appl. No.: 211,274

Assignee:

Foreign Application Priority Data Dec. 29, 1970 Japan 45-129134 US. Cl 96/l.5, 252/501, 75/134 H Int. Cl G03g 5/00 Field of Search 96/1 R, 1 PC, 1.5;

References Cited UNlTED STATES PATENTS 5/1956 Mengali 96/15 OTHER PUBLlCATlONS Keck, Photoconductivity in Vacuum Coated Selenium Films, J. Optical Soc. Amer., Vol. 42, No. 4, Apr. 1952, Pp- 221-225.

Primary Examiner-Roland E. Martin, Jr. Attorney, Agent, or FirmFitzpatrick, Cella, Harper & Scinto 5 7] ABSTRACT A photosensitive layer for electrophotography is composed of Se-Te alloy containing less than 3 percent by weight of Te and the Te is in a form of seleniumtellurium bond, and the Se-Te alloy has a polarity of N-type.

2 Claims, 1 Drawing Figure PATENTHuuu 11 m4 38-1-61 16 /i inmaseca 1 N-TYPE PHOTOSENSITIYE MEMBER FOR ELECTROPHOTOGRAPHY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an N-type photosensitive member comprising Se-Te alloy. for electrophotography and a process for preparation thereof.

2. Description of the Prior Art In general, conventional Se-Te alloy containing a large amount of Te gives a panchromatic photosensitive member of P-type of high sensitivity when vapor deposition of Se-Te alloy is effected by keeping the temperature of a substrate higher than 60C, particularly, at 65 to 68C. On the contrary, when the substrate temperature is lower than 60C, tendency of P- type decreases while tendency of N-type increases and there is produced a thermally unstable and inpracticable photosensitive member. However, in such a case, there is not obtained a photosensitive member showing N-type only.

A stable and highly sensitive photosensitive member of N-type is very useful, but a method for preparing such photosensitive member is not yet developed.

SUMMARY OF THE INVENTION In accordance with theone aspect of the present invention, there is provided a photosensitive layer for electrophotography which comprises Se-Te alloy containing less than 3 percent by weight of Te, the Te being in a form of selenium-tellurium bond, and the Se-Te alloy having a polarity of N-type.

In accordance with another aspect of the present invention, there is provided a photosensitive member for electrophotography comprising a base plate and a photoconductive layer overlying the base plate and composed of Se-Te alloy containing less than 3 percent by weight of Te, the Te being in a form of seleniumtellurium bond and the Se'Te alloy having a polarity of N-type, and if necessary, an insulating layer overlies the photoconductive layer.

In accordance with a further aspect of the present invention, there is provided a process for producing a photosensitive layer for electrophotography which comprises producing a selenium-tellurium alloy containing less than 3 percent by weight of tellurium, containing Se-Te bond and showing N-type polarity by depositing selenium and tellurium on a substrate maintained at a temperature of 60-70C.

It is an object of this invention to provide an N-type photosensitive member of excellent durability, good image shapeability, and high sensitivity.

It is another object of this invention to provide a process for producing an Se-Te alloy photosensitive layer for electrophotography of high stability and high sensitivity.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a graph showing decay curves for a photosensitive member of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an Se-Te alloy photosensitive member of N-type is obtained by adjusting the contents of'Te to less than 3 percent by weight.

It has been found that the tellurium contents in an Se-Te alloy affects the polarity (i.e., N-type or P-type) as shown below. At tellurium contents of about 3 percent by weight there appears a boundary. In other words, when the tellurium content exceeds 3 percent, both N-type tendency and P-type tendency coexist, and the higher the tellurium content, the stronger the P- type tendency, and there is not obtained an N-type tendency as desired in the present invention. On the contrary, when the tellurium content is less than 3 percent, the N-type tendency increases and there is obtained an Se-Te alloy photosensitive layer as contemplated in the present invention. Particularly at tellurium content less than 1 percent there appears strong N-type tendency. When the tellurium content becomes less than 0.01 percent, the N-type tendency disappears.

The photosensitive layer is produced by depositing selenium and tellurium on a substrate maintained at a temperature of 6070C to form a selenium-tellurium alloy containing less than 3 percent by weight of tellurium, containing Se-Te bond and showing N-type polarity. When the temperature is higher than C, there occurs crystallization, and when the temperature is lower than 60C, the resulting Se-Te alloy layer shows both tendencies of N-type and P-type.

For the purpose of the present invention, the tellurium should not be present as an component of a simple mixture of Se and Te, but in a form of Se-Te bond in an Se-Te alloy.

In the following cases, the Se-Te alloy shows P-type tendency under the same conditions regardless of the state of materials used for deposition:

1. a commercially available pure selenium is directly deposited;

2. a commercially available selenium is melted at 450C for 3 hours and quenched, and the resulting selenium is deposited;

3. a commercially available selenium is melted at 450C for 3 hours and cooled gradually to room temperature in a period of 15 hours and the crystalline selenium thus obtained is deposited.

On the other hand, when Te is deposited after Se is deposited, for example, 39.8g. of commercially available selenium is deposited while keeping the substrate temperature at 66-68C and then 0.2g. of commercially available tellurium is deposited thereon, or a mixture of 39.9g. of selenium and 0. lg. of tellurium is deposited in a way similar to above, the resulting plate shows low resistance and cannot be used for electrophotography.

As is clear from the above fact, in the Se-Te alloy used in this invention the Te should not be in a form of a simple mixture of Te and Se, but in a' form of Se-Te bond. For example, uniform concentration of Te is to be maintained in a process of production of the Se-Te alloy to give Se-Te bond.

The following examples are given for illustrating the present invention, but by no means for restricting the present invention.

EXAMPLE I Fine nine selenium 99.4g. and tellurium 0.6g. were placed in a Pyrex glass tube, and air was evacuated until the pressure became 10' Torr. and then the tube was sealed. The metals were heated at 550C for 4 hours with stirring by shaking every 10-15 minutes, then gradually cooled to about 250C and quenched to about 300C 6668C l Torr.

35 minutes temperature of vapor source temperature of substrate vacuum depositing time The resulting deposit layer was negatively charged at 1,000 V, imagewise exposed by using an original having light and dark portions at exposure amount of lux. sec. (illuminance, about 40 lux. sec.) and the surface potentials were measured. The result is illustrated in F 1G. 1. The curve 1 shows decay at a dark portion and the curve 2 shows decay at a light portion when the photosensitive member is positively charged. The curve 3 shows decay at a dark portion and the curve 4 shows decay at a light portion when the photosensitive member is negatively charged.

As is clear from curve 3 in the graph, when the photosensitive member is negatively charged, decay at a dark portion is very little, and it is clear that there is shown more N-type property.

EXAMPLE 2 That is, the photosensitive member was charged (primary charge), imagewise exposed simultaneously discharged by AC, and subjected to blanket irradiation to form electrostatic images. The conditions were as shown below:

about 2300V (surface potential) Primary charge secondary discharging AC voltage exposure amount at light portion l5 lux. sec. exposure amount of blanket irradiation lux. sec.

The result is shown below.

Surface potential Surface potential Contrast (V) at light portion (V) at dark portion (V) EXAMPLE 3 The procedures of Example 2 were followed except employing corona discharge of polarity opposite to that of the primary charging in place of AC discharging. The conditions were as shown below:

about 2300V (surface potential) primary charge secondary discharging 750OV exposure amount at light portion 15 lux. sec. exposure amount of blanket 150 lux. sec.

irradiation Surface potential Surface potential Contrast (V) at light portion (V) at dark portion (V) We claim:

sulating layer overlaying the photosensitive layer. 

2. A photosensitive member comprising the photosensitive layer prepared according to claim 1 and an insulating layer overlaying the photosensitive layer. 